The present invention relates to hand tools, and more particularly to hand-held cordless or corded adhesive dispensers using electrically generated heat to melt the adhesive, which is in stick form. Such tools are commonly referred to as xe2x80x9cglue guns.xe2x80x9d
Glue guns are well known in the art, and various configurations for corded glue guns are illustrated in the following U. S. Pat. Nos.: 3,604,597, issued Sep. 14, 1971 to Harold E. Pohl et al.; U.S. Pat. No. 4,523,705, issued Jun. 18, 1985 to Richard W. Belanger et al., and U.S. Pat. No. 5,215,230, issued Jun. 1, 1993 to Grace Lee. In all of these patents, an electrical supply cord is permanently attached to the handle of the glue gun to provide, on demand, electrical current to a heater in the gun to melt a portion of an adhesive which is then expelled through a nozzle at the outer end of the xe2x80x9cbarrelxe2x80x9d of the glue gun. Such corded guns for direct connection to an electrical power outlet by an electrical cord are well known in the art and are widely sold throughout the world at present in many different configurations.
A variation of this type of electrical current supply is shown in U. S. Pat. No. 4,826,049, issued May 2, 1989 to Howard D. Speer, in which the gun is placed in a base containing the electrical current source, and the melting of the adhesive occurs while the gun remains in the base. Removal of the gun from the base terminates the flow of the current through the heating element utilized to melt the adhesive.
Cordless type glue guns differ from the preceding types in that the gun contains a power source, a rechargeable battery, which is used to supply the current, on demand, to melt the adhesive. Such guns normally include a stand which contains a battery recharging circuit connected to a source of electrical power, so that when the gun is replaced in the stand after use, the battery is recharged. Such cordless guns and recharging systems are well known in the art and are widely sold throughout the world at present in many different configurations.
Whether corded or cordless, all glue guns have certain characteristics in common. They have a hand gun-like shape with a pistol grip which is grasped by the user when the gun is in use. The gun contains an electrical heater element, typically located in the gun xe2x80x9cbarrel.xe2x80x9d The adhesive is in a solid stick form which extends through the barrel adjacent the heater element and is xe2x80x9cmeltedxe2x80x9d by the selective application of electrical power to the heater element. Application of the electrical power is controlled by a trigger mechanism. The gun barrel terminates in a nozzle, through which the molten adhesive is extruded by pressure applied to the adhesive stick by one or more of a variety of linkages actuated by actuation of the gun trigger. The nozzle typically includes a spring-loaded ball check valve in an effort to terminate the flow of molten adhesive as soon as pressure on the trigger is released, in an attempt to avoid molten adhesive dripping from the nozzle thereafter.
Corded and cordless glue guns each have their own advantages with respect to one another. For example, cordless guns provide portability for use on sites remote from an electrical outlet, while corded guns provide for continuous use without the necessity of recharging or changing the battery. Consequently, a user may utilize one of each type of gun to provide for maximum flexibility in performing work.
According to the present invention, a glue gun, suited for either cordless or corded operation, has a gun casing with a base and a barrel, the base being adapted to receive electrical power from a power source which is either a battery or an ac to dc converter; a heater element housing containing a heater element; a drive motor; electrical circuit means for applying electrical power to the heater element and to the drive motor; a feed roller disposed within the casing so as to be transverse to and in longitudinal alignment with the barrel and operable, in response to the selective application of electrical power to the drive motor, to be rotated thereby in a preselected direction, the barrel terminating in a nozzle remote from the feed roller; a removable glue stick holder disposed within the barrel in axial alignment with and between the nozzle and the feed roller so that a glue stick, when disposed within the glue stick holder, extends from the nozzle through the glue stick holder onto and beyond the feed roller; and a pinch roller for pressing the glue stick, when so disposed, against the feed roller when electrical power is applied to the drive motor, to assist in the urging the glue stick toward the nozzle in response to rotation of the feed roller in the preselected direction. In the presently preferred embodiment, the glue stick holder, which extends through the heater element, includes a peripheral stop ring to prevent the glue stick, as it is being fed toward the nozzle, from moving the glue stick holder through the heater.